To communicate and/or provide power between a platform such as an ocean vessel and a remotely operated vehicle (ROV) being deployed from it, a signal-carrying umbilical is often needed. Such umbilicals most often employ fiber optics or electrical conductors as signal carriers. The performance requirements to transmit data and/or power within the umbilical are often such that very light gauge materials may be used. Such materials while suitable signal carriers are generally not useful for load bearing operations.
Other tethering systems including cables, moorings, umbilicals, support harnesses, and straps are useful for lifting, disposing, operating, and securing marine equipment particularly in the ocean or large bodies of water. Used in a variety of different fields such as oceanographic research, offshore oil industries, military operations, and underwater salvage and rescue, the tethered marine equipment often includes remotely operated vehicles (ROVs), unmanned underwater vehicles (UUVs), submarines, mini submarines, observatories, and other heavy loads which may require additional reinforcement to properly support such weights.
In operation, these heavy marine loads are often lifted from a sea-, offshore-, or land-based platform such as a ship or a dock, hoisted into the air, and lowered from the platform into the body of water. In order to accomplish the deployment, operations, and recovery of the marine load, a tether system may be engaged with a retraction device such as a winch to haul in the marine load from the water. Conventional cables and tethers are often comprised of steel and as the weight of the marine load increases, so must the diameter and length of the steel cable which itself increases significantly in weight. Furthermore, the heaving up and down motions of the water produced by waves during deployment and recovery of the marine load can damage both the tether system and the attached load. Other tethering systems may utilize high strength materials such as Kevlar in the entirety of the tether; however, Kevlar tethering systems or the like are very expensive, lack flexibility, and are often limited in lifespan.
To alleviate these problems, specialized tethers or reinforced cable modifications are designed for the deployed vehicle to prevent breakage under the weight of the load and stress forces applied to the tether. Many conventional tethers may be designed to handle the weight of the load, but may not be properly equipped to manage the torsional forces induced by the operation of the marine load, resulting in undesired hocking or twists in the tether. Individually modified setups for each marine load can be fairly expensive and may not be suitable for all operations. Furthermore, the addition of more modifications and supports add significant weight to the cable which may not be conducive to the operation of the marine load.
Incorporation of signaling—(including power—) carrying capability into complex load bearing marine tethers both complicates the tether design and the expense of tether design manufacture and operation. Therefore, there exists a need for a lightweight adaptable lifting tether system which can not only be easily adapted to lift, dispose, and retrieve a plurality of marine vehicles and equipment but fits the power and communication needs of the marine load. Such an adaptable tether would also need to be capable of relieving torsional forces to prevent damage and breakage of the tether system and/or signaling capability.